This application makes reference to and claims all benefits accruing under 35 U.S.C. Section 119 from an application entitled xe2x80x9cBit Rate Discrimination Device with Temperature Compensation Function,xe2x80x9d filed in the Korean Industrial Property Office on Aug. 22, 2000 and there duly assigned Ser. No. 2000-48502.
1. Field of the Invention
The present invention generally relates to a light transmission system, and, in particular, to a bit rate discrimination device for use in a light transmission system.
2. Description of the Related Art
A light transmission system can adopt various protocols, such as FDDI (Fiber Distributed Data Interface), ESCON (Enterprise Systems Connectivity), Fiber Channel, Gigabit Ethernet, and ATM (Asynchronous Transfer Mode) for high-bandwidth and high-bit-rate communications. Fiber optics technology can adopt various bit rates of 125 Mb/s, 155 Mb/s, 200 Mb/s, 622 Mb/s, 1062 Mb/s, 1.25 Gb/s, and 2.5 Gb/s to supply the capacity to meet the demand for multimedia applications. In operation, the light transmission system adopts one set of the protocols as a multiplexing format for using any number of bit rates. In this type of light transmission system, the bit rate of an optical signal is set previously to a specific rate, such that an optical receiver can be designed to match the incoming bit rate. The function of an optical receiver is to convert an input optical signal into an electric signal, and thereafter restores the electric signal to the original data that is noise-free.
FIG. 1 illustrates a conventional bit rate discrimination device, which includes a photoelectric converter 110; a signal processor 120; a bit rate detector 130; a DC (Direct Current) amplifier 140; and, a bit rate discriminator 150.
During operation, the photoelectric converter 110 converts an input optical signal into an electric signal 112. A photodiode is typically used for the photoelectric converter 110. The signal processor 120 amplifies the electric signal 112 into a standardized electric signal 122, such that a level xe2x80x9c0xe2x80x9d and a level xe2x80x9c1xe2x80x9d of the electric signal 122 have predetermined values, respectively. The bit rate detector 130 outputs a discrimination signal 132, representing the number of pulses proportionate to the bit rate of the standardized electric signal 122. The DC amplifier 140 outputs a bit rate detection signal 142 by amplifying the discrimination signal 132, wherein the voltage level of the bit rate detection signal 142 is linearly increased according to the bit rate. The bit rate discriminator 150 discriminates the bit rate of the optical signal between a xe2x80x9c1xe2x80x9d and a xe2x80x9c0xe2x80x9d from the voltage level of the bit rate detection signal 142.
However, the DC amplifier 140 of the conventional bit rate discrimination device, as described in the preceding paragraph, is very susceptible to variations in the operating temperature, making it difficult to stabilize its output. Hence, the bit rate discriminator 150 tends to inaccurately determine the bit rate of the optical signal depending on the unstable voltage level of the bit rate detection signal 142. As a result, it is difficult to accurately discriminate the bit rate by means of a bit rate discriminator.
The present invention is directed to a device that is capable of accurately discriminating the bit rate regardless of variations in the operating temperature.
The present invention provides a bit rate discrimination device with a temperature compensation function. The device includes a photoelectric converter for converting an input optical signal into an electric signal; a bit rate detector for detecting the bit rate of an optical signal from the electric signal and for outputting a discrimination signal indicating the bit rate; a DC amplifier for outputting a bit rate detection signal by amplifying the discrimination signal; a temperature detector for detecting the operating temperature of the DC amplifier and outputting a temperature signal indicating the detected operating temperature; a variation amplifier for outputting a temperature compensation signal by amplifying the voltage level difference between the temperature signal and a predetermined reference signal, so as to cancel variations in an output voltage of the DC amplifier according to the operating temperature; a voltage adder for outputting a temperature-compensated bit rate detection signal by combining the bit rate detection signal with the temperature compensation signal; and, a bit rate discriminator for determining the bit rate of the input optical signal according to the voltage level of the temperature-compensated bit rate detection signal.
According to another aspect of the present invention, a signal processor standardizes the electric signal output from the photoelectric converter, such that the voltage levels of xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d of the electric signal have predetermined values, respectively, thus providing the standardized electric signal to the bit rate detector.
According to another aspect of the present invention, the DC amplifier has a characteristic in which the voltage level of the bit rate detection signal is increased in proportion to an increase in the operating temperature. In addition, the variation amplifier has a characteristic in which the voltage level of the temperature compensation signal is decreased in proportion to an increase in the operating temperature of the DC amplifier.